Audio, video and computer magnetic recording tapes have magnetic recording layers that are given a smooth surface to provide higher sensitivity, particularly higher output in high-frequency ranges, as disclosed in, for example, U.S. Pat. No. 3,597,273. However, these smooth-surfaced magnetic recording tapes cannot be wound or rewound smoothly into a neat pack, and variations in tape tension reduce the running properties of the tape and cause fluctuations in tape output. Furthermore, these tapes are easily deformed or damaged. To eliminate these defects, a magnetic recording tape has been proposed that has a back coating on the surface of the nonmagnetic base opposite that having a magnetic recording layer. However, the conventional back coating is easily scraped, its wear coefficient is easily increased or edge bends will easily occur. In addition, the coating has high surface electrical resistance and easily accumulates static charges. As a result, small dust particles or scratches will cause dropouts ver easily. For these reasons, the conventional back coating needs further improvements. U.S. Pat. Nos. 4,135,031 and 4,135,032 proposed a magnetic recording tape having a back coating containing inorganic particles such as graphite, carbon black powder, etc. However, graphite and carbon black powder are easily scraped, so that the back coating has poor durability to running and causes dropouts after repeated use while the back coating does not cause dropouts at the initial stage since it has good electroconductivity. Further they are dispersed in a binder only with difficulty and are apt to form aggregates, encountering a problem in the formation of a back coating having a smooth surface.
It is general practice to form a back coating on a magnetic recording layer to provide better running properties and increased durability to running. However, as is known well, when the resulting magnetic recording medium is rolled into a tape pack or sheets of it are stacked, the unevenness of the surface of the back coating is transferred onto the surface of the magnetic layer, impairing the surface quality of the latter. As a consequence, the electromagnetic properties, particularly, the S/N ratio, of the magnetic recording medium are reduced. As is often observed, the back coating is given a rough surface so as to achieve the best running properties. However, this causes the unevenness of its surface to be transferred onto the surface of the magnetic layer while the magnetic recording medium is stored in the form of a tape roll or stacked sheets.